System and method of detection of power loss in powered ethernet devices
First Claim
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1. A powered device comprising:
- at least one power supply input responsive to an external power source;
a diode bridge having an input to receive the at least one power supply input; and
a power loss detector having an input responsive to the at least one power supply input, the power loss detector to detect a power loss event, and to initiate a power shutdown to turn off power to at least one circuit coupled to the diode bridge in response to detection of the power loss event, the power loss detector comprising;
at least one blocking diode responsive to the at least one power supply input;
a zener diode circuit including an input coupled to the at least one blocking diode and including an output, the zener diode circuit having a breakdown voltage characteristic that defines a voltage level related to the power loss event; and
a comparator coupled to the output of the zener diode circuit, the comparator to generate an output signal related to a voltage level of the at least one power supply input.
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Abstract
A powered device includes a power supply input, a diode bridge, and a power loss detector. The power supply input is responsive to an external power source. The diode bridge has an input to receive at least one power supply input. The power loss detector includes an input responsive to the power supply input. The power loss detector is adapted to detect a power loss event and to initiate a power shutdown. In one embodiment, the powered device includes a load circuit to receive a power supply voltage from the diode bridge. The load circuit is responsive to the power loss detector to perform a power shutdown operation.
24 Citations
18 Claims
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1. A powered device comprising:
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at least one power supply input responsive to an external power source; a diode bridge having an input to receive the at least one power supply input; and a power loss detector having an input responsive to the at least one power supply input, the power loss detector to detect a power loss event, and to initiate a power shutdown to turn off power to at least one circuit coupled to the diode bridge in response to detection of the power loss event, the power loss detector comprising; at least one blocking diode responsive to the at least one power supply input; a zener diode circuit including an input coupled to the at least one blocking diode and including an output, the zener diode circuit having a breakdown voltage characteristic that defines a voltage level related to the power loss event; and a comparator coupled to the output of the zener diode circuit, the comparator to generate an output signal related to a voltage level of the at least one power supply input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A powered device coupled to a network to receive power and data from the network via a cable, the powered device comprising:
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at least one power supply input responsive to a wire of the cable, the cable to provide data and power; a first supply terminal and a second supply terminal; a diode bridge having an input to receive the at least one power supply input and having an output to provide a rectified supply voltage to the first and the second supply terminals; an input filter capacitor coupled between the first supply terminal and the second supply terminal; and a power loss detector having an input responsive to the at least one power supply input, the power loss detector to detect a power loss event and to automatically initiate a power shutdown when a voltage level of the at least one power supply input falls below a threshold level; wherein the power loss detector is coupled to the first and second supply terminals, the power loss detector to clamp a voltage between the first supply terminal and the second supply terminal to produce a step voltage, wherein a falling edge of the step voltage comprises a power loss indicator. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method comprising:
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monitoring an input voltage at an input port of a powered device, the powered device including power circuitry responsive to the input port to rectify the input voltage to produce a rectified voltage supply; comparing the input voltage to a threshold voltage level; detecting a power loss event when the input voltage falls below the threshold voltage level; and clamping a voltage between the first supply terminal and the second supply terminal to produce a step voltage having a falling edge that represents a power loss indicator to initiate a power shutdown of associated circuitry in response to detecting the power loss event; wherein the power loss event is detected concurrently while the rectified voltage supply of the associated input voltage is being produced. - View Dependent Claims (16, 17, 18)
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Specification